Currently I have the Roush Off Road on my 07 5.4 SC. I will be doing high flow cats soon. My question is, would it be worth the effort and money to change out the section of pipe between the Y and the Roush Catback from 2.5" to 3"?

 

If you want a little more flow path and a hint more sound yes. The Roush kit comes with a bit of 3" pipe prior to it correct? Having the Y pipe chopped till the outlet is 3" and running 3" pipe directly to the Roush pipe would be a good conversion. Thats how I would run it, and with those hi-flow cats too.

 

That's what I was thinking. I'll just have the shop do it while putting in the HI-flows. Now I just need to make sure the shop carries 304 stainless to match the Roush or buy it before I go.

 

I could probably do this now using band clamps.

 

Could. You may get an exhaust leak if you use a pipe that flanges over the pipe going towards the muffler ( my cat delete pipes are flanged on both ends and both leak at the back ) if the flanges on my pipes were facing towards the front the flow would just go right through and nothing would seap out, but you can still do it, and have the shop weld them shut. One of these days i'll have my shop weld them shut.